This invention relates generally to temperature sensitive timing control devices for a toaster or the like appliance and more particularly to such a device employing both main and compensating heat sensitive bimetal elements for controlling the toasting time in a toaster appliance.
In conventional bread toasters of the "pop up" variety, which use a bimetal element heated by the bread being toasted to release a latch mechanism maintaining the bread carrier in a lowered position, the second, third, etc. toasting cycles, if instituted rather close in time to one another, tend to render the bread continually lighter in color. The latter occurs because the bimetal element controlling the time of the toasting cycles is not given sufficient time to cool between the cycles and as such subsequent toasting periods are shortened
To compensate for the above, compensating bimetal elements have been provided which respond to the toaster cavity temperature during the toasting cycle and act against the movement of the main bimetal element to force the latter to bend an even greater distance on subsequent cycles to release the bread carrier. In this fashion, the length of successive toasting cycles are controlled such that the toast color is maintained relatively constant. Such a compensating bimetal element arrangement is described in U.S. Pat. No. 3,350,997.
While arrangements such as that described heretofore for the most part, solve the problem of uneven duration of toasting cycles, they tend to upset the "reset time" of the toaster. The "reset time" is herein defined as the time required after a toasting cycle has been completed and the latching mechanism has becomes reengaged for use during subsequent toasting cycles. Too long a reset time is generally considered objectionable to a user.
One method used to avoid the reset time problem is to choose a main bimetal element which is relatively small in size and to provide a shield or additional member to absorb heat therefrom, thereby to more rapidly cool the bimetal element and thus permit it to return to a "reset" condition more quickly. Such arrangements are illustrated in U.S. Pat. Nos. 2,865,279 and 3,035,509. The drawback to the last-described devices, however, is that the size of the bimetal element makes it relatively "weak", thereby not being able to supply sufficient force to release the bread carrier latching machanism. Consequently, a more complex and costly latch release arrangement may be required to provide such force.